[PATCH] mmc: sdhci-esdhc-imx: implement reset quirks for i.MX6 DualLite/Solo

[Stefan Christ <s.christ@phytec.de>]

The ROM Code of i.MX6 Quad/Dual uses the MMC interfaces differently than
the i.MX6 Solo/DualLite when it loads the bootloader from the interface:

                Register DLL_CTRL(0x60)  Bit 25 FBCLK_SEL (0x48)
    Quad:       0x0                      0
    DualLite:   0x01000021               1

Since the linux kernel or bootloader driver doesn't reset all registers,
the MMC interface is in an inconsistent state, which leads to boot
failures for some eMMC devices on the i.MX6 DualLite SoC. The errors
look like:

    mmcblk1: error -84 transferring data, sector 0, nr 8, cmd response 0x900, card status 0xb00
    mmcblk1: retrying using single block read
    mmcblk1: error -84 transferring data, sector 2, nr 6, cmd response 0x900, card status 0x0
    blk_update_request: I/O error, dev mmcblk1, sector 2
    mmcblk1: error -84 transferring data, sector 3, nr 5, cmd response 0x900, card status 0x0
    blk_update_request: I/O error, dev mmcblk1, sector 3

The register DLL_CTRL is already reset. Reset also the bit FBCLK_SEL.

Signed-off-by: Stefan Christ <s.christ@phytec.de>
---
Hi,

this patch is a follow up to

    http://www.spinics.net/lists/linux-mmc/msg36331.html

    mmc: sdhci-esdhci-imx: disable DLL delay line settings explicitly

    Disable DLL delay line settings explicitly during driver initialization
    in case ROM/uBoot had set an invalid delay.
    e.g. MX6DL ROM has set the default delay line(DLLCTRL) to 0x1000021,
    the uSDHC clock timing will become marginal when works on DDR mode
    due to default delay and will possibly see CRC errors in case the board
    is not perfectly designed on the eMMC chip layout.
    
    Signed-off-by: Dong Aisheng <aisheng.dong@xxxxxxx>

It doesn't apply cleanly on Linus master branch, since the above patch is
missing.

Mit freundlichen Grüßen / Kind regards,
        Stefan Christ
---
 drivers/mmc/host/sdhci-esdhc-imx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
index 4490808..9101556 100644
--- a/drivers/mmc/host/sdhci-esdhc-imx.c
+++ b/drivers/mmc/host/sdhci-esdhc-imx.c
@@ -1191,6 +1191,10 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
 
 		/* disable DLL_CTRL delay line settings */
 		writel(0x0, host->ioaddr + ESDHC_DLL_CTRL);
+
+		/* reset bit FBCLK_SEL for i.MX6 Solo/DualLite ROM code */
+		writel(readl(host->ioaddr + ESDHC_MIX_CTRL) & ~BIT(25),
+			host->ioaddr + ESDHC_MIX_CTRL);
 	}
 
 	if (imx_data->socdata->flags & ESDHC_FLAG_MAN_TUNING)
-- 
1.9.1